At present solid state devices are extensively used in communication equipment wherein the devices are included in modular assemblies or are mounted on circuit boards which are electrically interconnected by connectors attached to multi-wire cables. These multi-wire cables may be secured to a connector by soldering or bonding operations that are adequate to attain the necessary electrical characteristics, but these securing operations are relatively weak and subject to failure upon mechanical pulling forces being imparted to the wires. During the assembling, testing, use and maintenance of these equipments, the connectors are frequently pulled from the modules and circuitboards. In order to protect the soldered joints, strain relief devices have been developed.
One type of connector commonly used in telecommunication equipment comprises a series of sockets located in a plastic housing which is secured to a small printed circuit board having an array of terminal pads onto which trailing conductive segments of sockets are solder secured. Cable wires are also solder secured to other terminal pads formed on the circuit board. The terminal pads are in the form of thin films of metal; hence, wires solder secured to such pads are susceptible to separation upon excessive pulling forces being imparted to the wires. In order to provide strain relief against pulling forces, a strain relief in the form of a bar has been developed, which bar is riveted and fixed to the circuit board.
The general problem of strain relieving soldered connections between wires and terminal pads on circuit boards has led to the development of several types of strain relief devices. In U.S. Pat. No. 3,622,943 to W. A. Reimer, there is disclosed a cable clamp mounted on a printed circuit board which consists of a pair of block halves having facing slots for accommodating and securing a section of sheathed cable. The block halves are secured together by screws and then the assembled block is secured to the printed circuit board by screw fasteners. In this device the cable sheath is collapsed around the wires to provide strain relief for the individual wires which are solder secured to terminals formed on the circuit board.
U.S. Pat. No. 3,907,396 to J. H. Huber shows a strain relief clamp comprising two bar-like members having inwardly directed lances. The bar-like members are secured together by screws so that the lances bite into the outer insulation of the cable to provide a mechanical strain relief. Another strain relief construction is shown in U.S. Pat. No. 4,130,334 to B. W. Anderson wherein a clamping bar is secured by screws against a flat cable. Spacers are interposed between the clamping bar and a termination plate to prevent excessive crushing of the insulation on the flat cable.